Car bucks, and shuts off after warming up and then won't start.?

Question

One day, my car would not start. I had it towed to a mechanic and they said it was the distributor cap and replaced and gave me the car. It seemed fine, but the next day after broke down on the highway. The engine just cut out, and I could not start it. I waited about 20 minutes and the car started. Brought it back to the mechanic and said just needed to re-tune it, however I am currently having the same issues.
(basically car starts up fine when cold but as soon as it warms up, it starts bucking at higher rpms and will then shut down and will not start until it cools off.) There is no indication of it overheating. The car is 10 years old with 190k miles so I don't want to spend a lot of money on it. Any ideas would be greatly appreciated.
Thanks,

1996 Geo Prizm LSi.
Thanks for all the replies so far.
(It was a AAA mechanic, however I think I pissed him off when I bought the parts myself.)

Also, I forgot to mention that the engine light came on just recently. (was still having the issue before it came on).

Answer 1

I need to know exactly what kind of car you have--year, make and model...obviously it's a '96 or so, but please specify. Acutally that sounds exactly like the Fuel Pump burning out. I had that problem last year. It would run fine all the way down the highway, but the moment I had to slow down and speed up again after it got hot, it quit and I had to pull over and wait about 20 minutes. This is because the coil on the pump motor is overheating and going bad. Can you hear a high pitched whining while driving, and if so, does this get louder or higher in pitch just before the car breaks down? You might also want to have your Fuel Pressure regulator checked. Sounds like your mechanic is a piece of dirt. I wouldn't go back to him.

P.S. Engines don't cool off in 20 minutes, but fuel pumps do. Since the ignition coil is sitting right on top of the engine, it's not going to cool down that fast. I've also had that problem. Once they over heat twice, or even once, they're gone. The reason for the bucking is the drop and surge of fuel pressure. When the fule pressure drops, the engine loses vacuum. The fuel pressure is regulated by vacuum, and when the engine drops, it also allows the pupm a second to start again. When the vacuum drops, it releases the fuel pressure regulator, sending another surge of fuel to the engine. I'm assuming you also have your foot down on the accelerator drying to get it going. With the butterfly wide open, plus this sudden surge of air, your RPM's will jump.

The best way to know if it is the Ignition Coil or the Fuel Pump, is obviously to have the resistance tested on your Ignition Coil, but if it happens to you again on the road, try pumping your accelerator and see if you can't get the car to go a little longer. If so, this is your Fuel Pump. Have it replaced(or do the job yourself, if you're bold and saavy. If you can't get it to go any further, whatsoever, it's probably the ignition coil.

If you want instructions on how to change the fuel pump, email me at [e-mail]

Ok, so A prism doesn't generally have problems with the fuel pump. But it is still a possiblilty, especially if you've never changed the fuel filter. This can put severe strain on the fuel pump. But I'm willing to be now that it's your ignition coil. I don't know who said you have electronic ignition, because by definition, you wouldn't have a distributor cap. Anyway, Have someone test your coil. Yeah you probably pissed the mechanic off by buying your own parts. I like AAA. But that doesn't mean he's not still a crook. I've run into so many of them, that's why I do everythign myself. If your coil is bad, you can change it yourself really easily. If your coil is fine, you CAN change your pump, but you REALLY don't want to. Especially if you don't have any way of getting the car into the air.

Answer 2

with out knowing the exact type of car it is, it's hard to say. If you provide more info, maybe able to shed some light on the situation. Need year, make, model and engine size.
But in this case it sounds like a fuel pump problem or an igniton module problem. If your car continues to show the same problems after they finish working on it. Take it to somebody else and get a second opinion. I would then call that shop and tell them that somebody else is fixing your vehicle and you'll be sending them the bill. I hate to say this, but always question what a mechanic tells you unless they have a really good reputation. I've been a mechanic for a long time and I for one know there's alot of idiots and crooked shops out there! I get alot of there customers!

Answer 3

You should tell what type of car it is!

OK, here's what I think:
You've electronic ignition in this vehicle (only 10 years old). It is my opinion that it starts and runs well until the ignition module heats/warms up. Whereupon the circuitry will short out and the car goes dead.

Take the car to an automotive electrician and have them run diagnostics on the system.

Answer 4

Try replacing the ignition coil It's heating up and causing resistance thus shutting off the engine then when cool it starts again

Answer 5

Sounds like the electronic ignition. Depending on what model your car is it can be a very easy do it yourself job. Its only a matter of plugging together a wiring harness. Auto Zone can help you.

Answer 6

Need more details about the vehicle. . ie year, make, model. you need to find out what (fuel, spark, other) that your losing. ive seen fuel pumps that after running awhile quit pumping fuel. have the technician install fuel pressure gauge and drive it till it acts up. this will condem or elliminate th efuel system. also look at fuel adaptives, if its a fuel related issue the adaptives will be high +25 or more.

Answer 7

All it is in my opinion is an ignition coil , not a distributor cap.When it gets warmed up it shortens out. Probable cause is water got in it or condensate accumulation. Change that thing , then see what it does.

Answer 8

it maybe the sensors if the computer sense that the car is over heated it might shut it off. but not sure for such a old car if these sensors were even put in.

Answer 9

HAHA You said "bucks" only horses buck. Now go shut the trailer door, your letting the a/c out.

Answer 10

The fuel pump filter is clogged or the pump itself is poorly. Both a cheap fix.